1. Field of the Invention
The invention concerns an apparatus and method for the continuous production of packaging wrappers from cut blanks of a flat material. More particularly, the invention concerns the continuous manufacture of packaging wrappers by gluing flaps in the cut blanks in an apparatus wherein the cut blanks are provided with gluing flaps arranged in a particular direction of passage and continuously passed along a track to an abrading station, a gluing station, and a folding station in general. It is an important feature of the invention that the abrading station precedes the gluing station to abrade the cardboard in the area of the gluing flaps for an improved design an improved adhesion.
A folding-box gluing machine of the type mentioned in the introduction hereto is known from the pamphlet "Construction Program" of the International Paperbox Machinery Co., of Nashua, New Hampshire (U.S.A.). The abrading device there is designed as a milling machine and serves to remove a uniform surface layer of the waxed or coated cardboard cut blanks in a flap area where gluing will take place. The abrading serves to remove or roughen the wax or the coating, which otherwise would interfere with the adhesion of the glue.
2. Background of the Prior Art
The invention has its origin in problems arising in the production of envelopes, wrappers or jackets for phonograph records. (The terms envelopes, jackets and wrappers will be used interchangably throughout the specification.) These envelopes have the form of unilaterally open, flat wrappers wherein gluing flaps connected with one of the covers of the wrapper fit against the inside of the other cover. This results in a step upon which the edge of the record disk comes to rest. This involves two disadvantages. The first consists of the fact that whenever the gluing flaps are even slightly loose at the insertion end, a user replacing the record envelope into the jacket will often insert the record between the flap and inside of the cover glued to said flap. The other, more significant, disadvantage occurs whenever the step formed by the gluing flap lies against the cover. In the case of a single record envelope in view of the prevailing cardboard thickness of 0.3 to 0.6 mm, the condition is not overly detrimental. However, whenever the records are stacked, the heights of the steps become additive and even with a stack of 100 disks, the difference in height at the edge and in the center will amount to several centimeters. This leads to the result that the disks will be suspended in the center and may result in permanent deformation of the disk. Today, this frequency occurs because more such disks are being manufactured from an especially thin material and practically possess no inherent stability. Obviously, disks deformed out of their plane are impaired in their ability to be played and often cannot be played at all.
Attempts have already been made to control the problem by trimming back the flaps to be glued internally to conform to the external circumference of the phonograph records. This method, however, did not provide much relief, because a small area of the gluing flap must be present at the external edge of the cutout to permit the satisfactory gluing of the disk envelope and, therefore, there still will be a step upon which the edge of the disk may settle.